In a few short texts, assigned to a mature period following a famous ‘conversion’ to Mahayana Buddhism, Vasubandhu argues that reality consists of ‘impressions-only’ (Siderits 2007), or ‘only appearance’ (Gold 2015). This prima faciemetaphysical idealism came to be known, famously and more simply, as the ‘Cittamatra’ view, which means ‘mind-only’.

Taking ‘external world’ to mean a world in space and time that is putatively independent of the mind, Vasubandhu argues that this conception is a delusion, one that imposes a crude conceptual grid on the field of experience. As a critic of ‘naïve realism’, Vasubandhu sees unchecked mental projections as imposing a spatiotemporal structure on experience which, once purged of this, can also be liberated from other forms of ignorance. In his Twenty-Verse Treatise, Vasubandhu considers various objections to this irrealist account of belief in an external world, responding by invoking e.g. analogies of dream-experience (and other intriguing anticipations of modern philosophy).

Shankaracharya, also known as Adi Shankara, is an 8th century Indian philosopher and theologian who argues that ultimate reality or brahman is single and not substantially distinct from the world. Often compared with Western monists such as Parmenides, Plotinus and Spinoza, Shankara contends that the universe of distinct particulars has only a dependent and limited being, and that our everyday attribution of ultimate reality to it is a result of ignorance. While in some respects this metaphysics resembles Buddhist emphases on the conditioned and transient nature of things, Shankara posits a stable and unchanging reality behind the shifting appearances, which is said to be identical with the permanent aspect of the self (atman) as pure consciousness. Shankara is a Vedantic thinker who respects the authority of the Upanishads, to which he appeals in support of his claims. However, his metaphysical position is at the same time developed through philosophical refutations of the views of rival schools, including Buddhist ones. Shankara’s commentary on the Brahma Sutras, for instance, contains arguments against Buddhist subjective idealism maintaining the non-existence of the external world, and against the central Buddhist doctrine of no-self or anatta.